In glass container forming machines, the containers typically are formed in two stages. At a first or blank mold stage, a charge or glob of molten glass is formed in a blank mold into a parison or preform. A neck ring is positioned adjacent to the blank mold, and the container neck finish is formed against the neck ring to final size and geometry. The parison then is transferred by means of the neck ring to a blow mold, in which the container body is formed to final size and geometry. The neck ring typically consists of two semi-circular neck ring bodies of cast bronze or steel construction.
It has been proposed in to assemble premade inserts to precast neck ring bodies to obtain more precise tolerances and wear resistance properties in the portions of the neck ring that contact the molten glass and form the closure attachment feature(s) of the container neck finish. However, there still remains a need to eliminate a specific commercial variation in the glass container as formed in the first or blank mold stage, known as a “hollow neck” variation, which is caused when insufficient heat is removed from the glass neck finish area at the parison forming stage. A general object of the present disclosure is to provide a neck ring and method of manufacture that achieves good wear resistance in the neck ring where it is needed most while drawing heat from the neck finish and minimizing the temperature gradient between the neck ring and the guide plate to reduce checks or other variations in this area. The neck ring bodies should also provide rapid heat removal from the glass in the non-attachment area of the finish being formed to thereby eliminate hollow neck defects.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
A neck ring for a glass container forming machine, in accordance with one aspect of the present disclosure, includes two semi-annular bimetallic neck ring halves. Each neck ring half includes an insert made of wear-resistant construction, such as nickel, bronze or steel, and a body of heat-conductive metal construction, such as bronze or steel, in which the insert is embedded. The cavity face of the neck ring thus includes a first portion formed by the wear-resistant inserts that are configured for molding closure attachment features in the container neck finish, and a second portion formed by the neck ring bodies configured for molding portions of the container neck finish that do not include the closure attachment features. The neck ring body material exposed at the second portion of the cavity face provides rapid heat extraction from the molten glass to reduce or eliminate hollow neck variations in the molded containers, while the material of the inserts at the first portion of the cavity face provides good wear-resistance.
A method of making a neck ring for a glass container forming machine, in accordance with another aspect of the present disclosure, includes first forming a finish attachment feature-forming component as a separate preform of wear-resistant material such as nickel, bronze or steel, and then embedding this feature-forming component into a body of heat-conductive metal construction, such as bronze or steel, that is provided with a surface for mold-forming the portion of the container neck finish that does not include the closure attachment features.